Many kinds of animals, including fish, show striking and consistent differences in how they respond to challenge. These differences are sometimes referred to as “temperament”. In common carp, a subset of fish are consistently active risk-takers while others are passive, risk-avoiders. Active carp have a higher resting metabolic rate than passive fish; they show a weaker physiological response to a standard stressor and different patterns of growth. When exposed to typical husbandry stressors, the two kinds of fish often show diametrically opposite responses in terms of which sets of genes are down-regulated or up-regulated. So temperament matters when it comes to production and ethical quality of farmed carp
